A critical factor in the clinical success of composite restorations is the durability of the dentin/adhesive bond. Current theories on dentin bonding suggest that two fundamental processes are involved in bonding an adhesive to dentin. First, the mineral phase must be extracted from the dentin substrate without damaging the collagen matrix and secondly, the voids left by the mineral must be filled with an adhesive resin that penetrates the exposed collagen. If the collagen collapses during this procedure it forms a barrier reducing the permeability of the decalcified layer and weakening the dentin/adhesive bond. Morphologic analysis of this bond frequently involves specimen preparation that may alter or even destroy the dentin/adhesive interface. Chemical analysis with techniques such as IR spectroscopy is confounded by the presence of water and the opaque nature of these samples. Raman spectroscopy is a light scattering technique that provides a "fingerprint" for the molecular species present within a sample. There is no spectral interference from water. When this technique is combined with a microscope compound, specific molecules can be detected at a lateral spatial resolution of 1mm. Background fluorescence has limited the application of Raman spectroscopy in the study of the dentin/adhesive interface. To avoid fluorescence this project will use a red excitation source, i.e., a Kr+ laser in conjunction with micro-Raman spectroscopy to characterize the chemical distribution of the adhesive and collagen across the dentin/adhesive interface. The overall hypothesis of this proposal is that demineralized dentin must be treated to resist collagen collapse and to provide resin infiltration into dentin thus stabilizing dentin/resin bonds. The following specific aims will be addressed: 1. to test the hypothesis that demineralized dentin can be stabilized such that it will resist collapse when air-dried by using organic solvents, specifically acetone, ethanol, and 2-hydroxyethylmethacrylate (HEMA); 2. to test the hypothesis that the collapsed collagen network will inhibit resin penetration as measured by mapping the chemical distribution of the adhesive and collagen across the dentin/adhesive interface; 3. to test the hypothesis that resin can penetrate a stabilized collagen network by recording changes in the Raman spectral features of the adhesive, collagen, and dentin across the dentin/adhesive interface; and 4. to test the hypothesis that resin penetration through a stabilized collagen network will reduce porosity at the dentin/adhesive interface.